Recently, the increasing consumption of electronic products and the global trend to promote the illumination technology has encouraged LED (Light Emitting Diode) and OLED (Organic Light Emitting Diode) to develop rapidly and caused them to replace the conventional lighting devices gradually. The development of LED and OLED also influences the spin-off industries, such as the industries massively using display panels. Development of OLED seems to be relatively slower than LED. However, OLED has advantages of self-luminescence, low power consumption, flexibility, high contrast and slimness. Therefore, the related manufacturers have all been devoted to researching and developing OLED.
An ordinary OLED, such as that disclosed by a US patent No. 2009/0295278, comprises an anode, a cathode, and an organic light emitting unit. The organic light emitting unit includes a hole transport layer connecting with the anode, an electron transport layer connecting with the cathode, and an organic light emitting layer arranged between the hole transport layer and the electron transport layer. While a bias is applied to the anode and the cathode, holes and electrons are respectively injected into the hole transport layer and the electron transport layer. The bias drives the holes and electrons to move and recombine in the organic light emitting layer, whereby light is emitted.
In the current OLED technology, the light emitting layer, electron transport layer and hole transport layer made of ordinary optoelectronic materials, such as the well-known α-NPB, Alq3, TPBI, etc., are insufficient to meet requirements of consumers. In order to solve the abovementioned problem, some manufacturers add extra layers to the existing light emitting layer, electron transport layer and hole transport layer to form a composite-structure OLED element and promote the overall performance thereof. Such a technology has a disadvantage: while an element malfunctions, the problem is hard to find out and solve quickly because of complicated structure. Further, the manufacturers have to spend considerable materials cost and fabrication cost in the composite-structure OLED, which makes the price hard to decrease and hinders OLED from replacing the conventional lighting elements.